Suspended superconducting transmission lines

ABSTRACT

Power transmission systems with cooling mechanisms, and methods of operating the same, are described. A power transmission system can include multiple support tower assemblies. Each of the support tower assemblies includes a support tower. One or more of the support tower assemblies includes a termination (i.e., a connection point via which electrical current and/or coolant can enter the transmission line and/or exit the transmission line). The power transmission system also includes multiple conductor assemblies suspended above a surface of the earth. Each conductor assembly includes an electrical conductor and is positioned between, and mechanically supported by, a pair of the support towers. The power transmission system also includes a coolant supply system that delivers a coolant fluid, during operation of the power transmission system, to at least one of the terminations, for cooling of the conductor assemblies.

RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application No. 63/115,140, filed Nov. 18, 2020 and titled“Suspended Superconducting Transmission Lines,” the disclosure of whichis hereby incorporated by reference herein in its entirety.

FIELD

The present disclosure is related to the field of electricitytransmission, and more specifically, to the distribution of alternatingcurrent (AC) or direct current (DC) electrical power using overhead,suspended transmission lines.

BACKGROUND

Electric power is typically moved from its point of generation toconsumer loads using an electric power grid (“the grid”). Electric powergrids include components such as power generators, transformers,switchgear, transmission and distribution lines, and control andprotection devices.

SUMMARY

Embodiments described herein relate to power transmission systems withcooling mechanisms, and methods of operating the same. In someembodiments, a power transmission system includes multiple support towerassemblies. Each of the support tower assemblies includes a supporttower. One or more of the support tower assemblies includes atermination (i.e., a connection point via which electrical currentand/or coolant can enter the transmission line and/or exit thetransmission line). The power transmission system further includesmultiple conductor assemblies suspended above a surface of the earth.Each conductor assembly includes an electrical conductor and is disposedbetween, and mechanically supported by, a pair of the support towersfrom the plurality of support towers. Each conductor assembly includes asuperconducting current carrying element, and is configured to receive acoolant flow to maintain the superconductor material within atemperature range below an ambient temperature. In some embodiments,each conductor assembly can optionally include a thermally insulatingjacket (also referred to herein as a thermal insulation jacket) (“TIJ”)to contain the coolant flow. In some embodiments, the thermal insulationjacket is not electrically isolated from an operating voltage of thepower transmission system. The power transmission system furtherincludes a coolant supply system that delivers a coolant fluid, duringoperation of the power transmission system, to at least one terminationfrom the plurality of terminations for cooling of the conductorassemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing components of an examplesuperconducting overhead power transmission system, according to anembodiment.

FIG. 2 illustrates a superconducting OH power transmission system,including an OH power transmission line and associated subsystems,according to an embodiment.

FIG. 3 shows a perspective view of a section of a conductor assembly fora superconducting OH power transmission line/system, according to anembodiment.

FIG. 4 shows a perspective view of a section of a conductor assembly fora superconducting OH power transmission line/system, includingelectrical insulation adjacent to one or more superconductors(superconductor wires or tapes) and disposed within a TIJ, according toan embodiment.

FIG. 5 shows a perspective view of a section of a conductor assembly fora superconducting OH power transmission line/system, includingelectrical insulation disposed exterior to a TIJ, according to anembodiment.

FIG. 6 shows a perspective view of a section of a conductor assembly foruse in a superconducting OH power transmission line/system, including acoolant tube, according to an embodiment.

DETAILED DESCRIPTION

Embodiments described herein relate to power transmission systems withsuperconductor cables and cooling mechanisms, and methods of producingand operating the same. Superconductor cables employed in powertransmission systems, as set forth herein, can operate at up to 10 timesthe current of conventional wire while maintaining superconductivity.Higher current allows for lower voltage and smaller rights-of-way.Additionally, energy can be transferred through power transmissionsystems at a higher rate through narrow rights-of-way with reducedenergy losses, as contrasted with known systems. Moreover, byincorporating active cooling mechanisms into power transmission systemswith superconductors, power transmission lines of the present disclosurecan exhibit reduced sag and creep and/or more consistent sag and creepover time, as contrasted with known systems. In other words, powertransmission lines of the present disclosure may exhibit sag and/orcreep that are not variable, or that do not substantially vary, overtime, in view of the actively controlled temperature of the powertransmission lines.

Known electric power transmission systems use continuous electricalconductors to interconnect power generation stations with consumerloads. Power generation stations, such as thermal (e.g., steam-driven),nuclear, hydroelectric, natural gas, solar and wind power plants,generate electric energy at AC voltages typically ranging between 15 kVand 25 kV. To transport the energy over long distances, the associatedvoltage is increased at the power generation station, for example via astep-up transformer. Extra-high-voltage (EHV) power transmission linescan transport the energy to geographically remote substations atvoltages of 230 kV and above. At intermediate substations, the voltagecan be reduced to high-voltage (HV) levels via a step-down transformer,and the energy is transported to HV substations via power transmissionlines that operate at voltages ranging from 220 to 110 kV. At HVsubstations closer to the loads, the voltage is further reduced to 69kV, and sub-transmission lines connect the HV substations to the manydistribution stations. At the distribution substations, the voltage isreduced to a value in the range of 35 kV to 12 kV before beingdistributed to the loads at 4160/480/240/120V via pole-top orpad-mounted step-down transformers. The precise voltages used intransmission and distribution vary slightly in different regions anddifferent countries.

In the United States, an EHV power transmission line has a nominalvoltage of between 230 kV and 800 kV, and a HV power transmission linehas a nominal voltage of between 115 kV and 230 kV. For voltages ofbetween 69 kV and 115 kV, the line is considered to be at asub-transmission level, and below 60 kV it is considered to be at adistribution level. The voltage values demarcating these designationsare somewhat arbitrary, and can vary depending on the authority havingjurisdiction and/or the location. Known EHV power transmission lines cantransport energy as far as 400-500 miles, whereas HV power transmissionlines can transport energy as far as 200 miles, and sub-transmissionlines can transport energy for 50-60 miles. High-voltage DC (HVDC) powertransmission lines are used to transmit energy over long distances orunderwater. In a HVDC system, AC voltage generated by a generator isrectified, and the energy is transmitted via a DC cable to the receivingstation, where an inverter is used to convert DC voltage back to AC.

As described above, electrical conductors are used to form a continuousconnection between the generators and the consumer loads (the “load”).The electrical conductors can include bus bars, underground cables,and/or overhead (i.e., physically suspended) lines (both transmissionand distribution), as appropriate. Overhead (“OH”) power transmissionlines are primarily used in open corridors or along wide roads, whereasunderground cables may be used in congested areas of densely populatedcities. OH transmission systems include a system of supportingstructures such as towers or poles (also referred to as “pylons”) thatsupport the electrical conductor above the ground. OH power transmissionsystems also include dielectric insulators that mechanically connect theconductor to the tower while keeping them electrically isolated from oneanother and from the tower, and elements to provide electrical groundand mechanical integrity. Elements that provide electrical ground andmechanical integrity can include structural foundations, groundingelectrodes, and shield conductors. Each supporting structure can be ofone of the following types: (A) pass-through/continuity (i.e., providingcontinuity of coolant flow and continuity of power transmission, withoutan auxiliary coolant inlet or outlet, and without performing re-cooling,re-pressurization, or flow control of the coolant); (B) flowsupplementing (i.e., providing continuity of coolant flow and continuityof power transmission, and including an auxiliary coolant inlet and/oroutlet, but without performing re-cooling, re-pressurization, or flowcontrol of the coolant); (C) coolant processing (i.e., providingcontinuity of coolant flow and continuity of power transmission, andperforming re-cooling, re-pressurization, or flow control of thecoolant, but without an auxiliary coolant inlet or outlet); or (D)combination (i.e., providing continuity of coolant flow and continuityof power transmission, with an auxiliary coolant inlet and/or outlet,and performing re-cooling, re-pressurization, and/or flow control of thecoolant). OH transmission systems set forth herein can include anycombination of supporting structures A, B, C, and D or of subsetsthereof. The supporting structures can have any of a variety of designsdepending on, among other considerations, the voltage of the powertransmission line, the location, and/or the requirements of localgovernments or other regulatory authorities. Example designs include:lattice or tubular towers, cantilevered or guyed poles and masts, andframed structures. Materials used to fabricate such supportingstructures can include, for example: galvanized steel, concrete, wood,plastic and/or fiberglass composite(s).

Conductors for OH power transmission lines can be bare metal (e.g.,copper, aluminum, or a matrix of aluminum and steel), or they can becoated or wrapped with an electrical dielectric insulation. Bare metalconductors are less expensive than insulated conductors, and thus aregenerally preferred in OH power transmission lines. Although aluminumhas a lower electrical conductivity than copper, it is more commonlyused in OH power transmission lines, due to its lower cost and lighterweight. To increase the mechanical strength of aluminum conductors,steel strands can be introduced into the conductor core, thereby forminga composite conductor. The aluminum conductor steel-reinforced (ACSR)conductor is currently the most common conductor used in OH powertransmission lines. Recently, “high temperature, low sag” conductorscomprising a matrix of aluminum and composite materials and/or othermetals have also been deployed in grids. Dielectrically insulated OHconductors are much more common in the distribution regions of the gridand at lower voltages (e.g., below 25 kV). Underground conductors aretypically covered with electrical insulation to prevent electricalcontact with other conductors or the ground/soil.

Bare OH conductors, when used in OH power transmission systems, aretypically suspended from poles or towers, supported by insulators, anddesigned to maintain a prescribed minimum clearance with respect to theground/soil, vegetation, and other structures. Surrounding air istypically the electrical insulation medium employed in bare OH conductorsystems. In other words, no additional structures are fixed to bare OHconductor systems. The insulators can be attached to the poles or towersin a variety of different configurations, depending on the type andlocation of the pole/tower. Insulators can be fabricated from a varietyof different materials, such as ceramic, porcelain, glass, andcomposite(s). Insulators are designed and selected to withstandelectrical, mechanical, and environmental stresses. Over the life of thepower transmission line, electrical stresses can be generated within theinsulators due to continuous operations and the associated temporaryovervoltages produced by switching, faults, and lightning. Mechanicalstresses can also be generated within the insulators, as a result of theconductor dead weight, ice formation, and wind loading. Environmentalstresses can impact both the electrical performance and the mechanicalperformance of insulators, and can be caused by ambient temperaturefluctuations, UV radiation, rain, icing, pollution, and altitude.

When suspended by support structures, a conductor typically exhibits acurved shape, with a minimum clearance to ground occurring at some pointbetween the two closest suspension poles or towers. The minimumclearance to ground, or to other energized parts, is typicallydetermined by the engineering standards adopted for the location (e.g.,state or federal), and depends on the voltage of the transmission line.Higher voltage lines typically have a greater specified minimumclearance to ground, and consequently use higher suspension poles ortowers.

Known OH conductors have a non-zero electrical resistivity. When aconductor is carrying power, the electrical current generates heat andthe conductor temperature rises above the ambient temperature. Theelectrical resistance of the conductor increases linearly withincreasing temperature, and thus the associated resistive losses (I²R)and can be significant at high power levels. Such losses can also limitthe power that a conductor can carry, as conductors have maximumoperating temperatures determined by the properties of their componentmaterials. Operating at excessively high temperatures can cause thematerial properties of the conductor to degrade over time.

Due to thermal expansion, elevated conductor temperatures can cause thelength of the conductor to increase, thereby reducing the clearance toground (i.e., increasing ‘sag’). Conductors can also elongate, or“creep,” over time due to tension, resulting in a permanently increasedsag. This increased sag may be taken into account when determining theminimum clearance to ground during installation of the conductor. Themaximum current or power that causes the conductor to reach the maximumallowable sag is known as a “thermal limit.”

Many OH conductors have a manufacturer-imposed upper operatingtemperature limit of 75° C. The maximum rated current for a givenoperating temperature limit, under prescribed conditions of ambienttemperature and wind, is known as the ampacity. OH conductors aretypically available with rated ampacities to 2,000 amperes (2,000 A) at75° C. Some ‘high temperature’ conductors can be safely operated up to atemperature of 225° C. without permanent damage or excessive sag. Theenergy losses of maintaining a transmission line at 225° C. overhundreds of miles in length are, however, large.

The “physical thermal limit” of an OH transmission line refers to theamount of power the OH transmission line can transport before reachingits maximum operating temperature. The physical thermal limit can dependon ambient conditions such as atmospheric temperature, sun, wind, timeof day (angle of the sun), etc. It is difficult for an operator of theOH transmission line to know the conditions at all locations of the OHtransmission line in real time, so the thermal limit is often setconservatively, leading in some cases to transmission lines beingsignificantly underutilized as compared to a scenario in which “dynamic”limits could be used.

In view of the foregoing, it is desirable to increase ampacities toincrease the power carried at a specified voltage. It is furtherdesirable to reduce the overall energy losses in transmitting electricalpower, to avoid the use of more expensive higher operating temperaturematerials. It is further desirable to remove the effects of environmenton the capacity limits of the transmission line, to allow maximumutilization. The acquisition and permitting of rights of way for powertransmission lines is one of the major impediments to installing newpower lines or increasing the capacity of existing lines. As such, whendesigning new transmission lines, ensuring compatibility with anexisting system voltage specification (e.g., of an existing transmissionline) facilitates the re-use of existing rights of way, thereby reducingcosts. The width of the right of way depends on the tower height and,hence, operating voltage. Operating at lower voltages for a given powerfacilitates the use of shorter towers or poles, thereby reducingenvironmental impacts and potentially increasing public acceptance.

In some applications, it is desirable to electrically insulate aconductor to reduce its potential to initiate fires. Enclosing aconductor in electrical insulation can also thermally insulate theconductor, however, thereby increasing its temperature for a given powerdissipation. This reduces the ampacity of a thermally limited conductorand hence the power for a given voltage.

Some electrically insulated conductors include a second conductor layerat ground potential (or negative system voltage) outside the insulator.If this outer ‘shield’ conductor has the same ampacity as the inner(“core”) conductor and the circuit is arranged so that it always carriesthe same current as the core but with the opposite polarity, then theexternal magnetic and electrical fields are always zero. A currentcarrying shield can also act to reduce the self-inductance of theconductor with potential system benefits. A shield with nonzeroelectrical resistance, however, will generate heat when carryingcurrent, thus reducing the thermal limit of the system.

In view of the foregoing, there is a need for transmission line systemsthat can carry AC power and/or DC power at currents higher than those ofknown systems discussed above and/or at voltage levels lower than thoseof known systems, that can be suspended from poles or towers, whosepower capacity is substantially independent of the environmentalconditions, whose power/energy losses to heat are lower, that havereduced visual impact, and that utilize narrower rights of way for agiven power rating. The conductors of such transmission line systems maybe electrically insulated and, optionally, include a shield layer thatdoes not significantly reduce ampacity. Such transmission line systemsare the subject of the present disclosure.

According to some embodiments, a system for transporting AC electricalpower or DC electrical power includes suspended, OH power transmissionlines constructed using one or more superconducting materials, andexhibiting reduced energy losses which may be time-shifted. The systemalso includes thermal insulation and a coolant that flows duringoperation, to maintain the superconducting materials at a specifiedoperating temperature. Mechanical components of the system are selectedbased on their mechanical properties being sufficient to physicalsuspension of the OH power transmission lines.

In some embodiments, a power system for transporting AC electrical poweror DC electrical power via a suspended, overhead power transmission lineincludes a conducting element having a plurality of wires (also referredto as “tapes”). The plurality of wires include at least onesuperconductor. The power system also includes a thermal insulationjacket (“TIJ”) to minimize an amount of heat that reaches the conductorfrom the surroundings of the conductor. The TIJ can be maintained at asystem voltage level, or can be electrically grounded. The power systemalso includes a mechanical tensile support element, disposed within theTIJ, to support the conductor and to suspend the conductor off theground, for example in the manner of an overhead power transmissionline. The power system also includes a coolant supply system configuredto cool the superconductor to a predefined operating temperature duringoperation of the power system, and to maintain the operating temperaturewithin a predefined temperature range by removing heat generated withinthe power system during operation of the power system and/or heatentering the power system during operation of the power system. Thepower system also includes a coolant delivery and conditioning systemconfigured to deliver coolant fluid (e.g., liquid, gas, or a combinationof liquid and gas) to one or more locations (e.g., a start end, aterminal end, and/or intermediate point(s)) of the transmission line bycausing the coolant fluid to flow into and along the transmission line.The power system also includes a plurality of terminations via whichelectrical current and/or coolant can enter the transmission line and/orexit the transmission line. In one or more embodiments, the power systemcan also include one or multiple intermediate conditioners (alsoreferred to herein as “re-cooling stations” or “intermediate coolingstations”) where the coolant is maintained at operating temperature(s)and pressure(s). The intermediate conditioners can be maintained at thesystem voltage level and isolated from ground potential, or theintermediate conditioners can be maintained at ground potential. Inother embodiments, no intermediate conditioners are included in thepower system. The power system also includes a venting system that iscollocated with the re-cooling stations and/or at least a subset of theplurality of terminations, and is configured to vent excess vapor(s),produced by the coolant, to atmosphere. The power system also includesone or more towers and/or poles configured to support the transmissionline, and a plurality of dielectric insulators configured tomechanically support the transmission line on the tower(s)/pole(s), andto electrically isolate the transmission line from the tower(s)/pole(s).

Although functional elements are listed separately herein, it may beadvantageous to combine two or more functions into one element. Forexample, the mechanical tensile support could be formed from a portionof the TIJ. Implementation of embodiments described herein can aid inhigh-current power transmission over long distances with relatively lowlosses.

FIG. 1 is a block diagram showing components of a power transmissionsystem 100, according to an embodiment. The power transmission system100 includes tower assemblies 110A, 110B (collectively referred to astower assemblies 110), electrically coupled via a conductor assembly120. A coolant supply system 130 is fluidically coupled to the towerassemblies 110 and the conductor assembly 120. In some embodiments, thepower transmission system can include a superconducting OH powertransmission system.

In some embodiments, power can be input to the power transmission system100 from an external power grid or other external power source. Thepower is routed via one or more electrical connections to the towerassembly 110A. The power is then routed to the tower assembly 110B viathe conductor assembly 120. From the tower assembly 110B, the power canbe routed to additional tower assemblies 110 or to one or more consumerloads. As shown, the power transmission system 100 includes two towerassemblies 110. In some embodiments, the power transmission system 100can include any number of tower assemblies 110, depending upon theapplication and/or the distance over which the power is to betransmitted. In some embodiments, the power transmission system 100 caninclude at least about 2, at least about 3, at least about 4, at leastabout 5, at least about 6, at least about 7, at least about 8, at leastabout 9, at least about 10, at least about 20, at least about 30, atleast about 40, at least about 50, at least about 60, at least about 70,at least about 80, at least about 90, at least about 100, at least about150, at least about 200, at least about 250, at least about 300, atleast about 400, or at least about 450, or at least about 500, or atleast about 550, or at least about 600, or at least about 650, or atleast about 700, or at least about 750, or at least about 800, or atleast about 850, or at least about 900, or at least about 950, or atleast about 1,000, or at least about 2,000, or at least about 3,000, orat least about 4,000, or at least about 5,000, or between bout 5,000 andabout 10,000 tower assemblies 110. In some embodiments, the powertransmission system 100 can include no more than about 10,000, no morethan about 7,500, no more than about 5,000, no more than about 2,500, nomore than about 1,500, no more than about 1,000, no more than about 500,no more than about 450, no more than about 400, no more than about 350,no more than about 300, no more than about 250, no more than about 200,no more than about 150, no more than about 100, no more than about 90,no more than about 80, no more than about 70, no more than about 60, nomore than about 50, no more than about 40, no more than about 30, nomore than about 20, no more than about 10, no more than about 9, no morethan about 8, no more than about 7, no more than about 6, no more thanabout 5, no more than about 4, or no more than about 3 tower assemblies110. Combinations of the above-referenced number of tower assemblies 110are also possible (e.g., at least about 2 and no more than about 500 orat least about 10 and no more than about 50), inclusive of all valuesand ranges therebetween. In some embodiments, the power transmissionsystem 100 can include about 2, about 3, about 4, about 5, about 6,about 7, about 8, about 9, about 10, about 20, about 30, about 40, about50, about 60, about 70, about 80, about 90, about 100, about 150, about200, about 250, about 300, about 350, about 400, about 450, or about 500tower assemblies 110.

As shown, the power transmission system 100 includes one conductorassembly 120 providing an electrical coupling between the towerassemblies 110. In some embodiments, the power transmission system 100can include any number of conductor assemblies 120, depending upon theapplication and/or the distance over which the power is to betransmitted. In some embodiments, the power transmission system 100 caninclude at least about 1, at least about 2, at least about 3, at leastabout 4, at least about 5, at least about 6, at least about 7, at leastabout 8, at least about 9, at least about 10, at least about 20, atleast about 30, at least about 40, at least about 50, at least about 60,at least about 70, at least about 80, at least about 90, at least about100, at least about 150, at least about 200, at least about 250, atleast about 300, at least about 400, or at least about 450, or at leastabout 500, or at least about 550, or at least about 600, or at leastabout 650, or at least about 700, or at least about 750, or at leastabout 800, or at least about 850, or at least about 900, or at leastabout 950, or at least about 1,000, or at least about 2,000, or at leastabout 3,000, or at least about 4,000, or at least about 5,000, orbetween about 5,000 and about 10,000 conductor assemblies 120 providingelectrical couplings between tower assemblies 110 adjacent to oneanother. In some embodiments, the power transmission system 100 caninclude no more than about 10,000, no more than about 7,500, no morethan about 5,000, no more than about 2,500, no more than about 1,500, nomore than about 1,000, no more than about 500, no more than about 450,no more than about 400, no more than about 350, no more than about 300,no more than about 250, no more than about 200, no more than about 150,no more than about 100, no more than about 90, no more than about 80, nomore than about 70, no more than about 60, no more than about 50, nomore than about 40, no more than about 30, no more than about 20, nomore than about 10, no more than about 9, no more than about 8, no morethan about 7, no more than about 6, no more than about 5, no more thanabout 4, no more than about 3, or no more than about 2 conductorassemblies 120 providing electrical couplings between tower assemblies110 adjacent to one another. Combinations of the above-referenced numberof conductor assemblies 120 are also possible (e.g., at least about 2and no more than about 500 or at least about 10 and no more than about50), inclusive of all values and ranges therebetween. In someembodiments, the power transmission system 100 can include about 1,about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9,about 10, about 20, about 30, about 40, about 50, about 60, about 70,about 80, about 90, about 100, about 150, about 200, about 250, about300, about 350, about 400, about 450, or about 500 conductor assemblies120 providing electrical couplings between tower assemblies 110 adjacentto one another.

Each of the tower assemblies 110 may include an associated dielectricinsulator (not shown). Each of the tower assemblies 110 also includes atower or other mechanical support structure (not shown). One or more ofthe tower assemblies 110 include a termination via which electricalcurrent and/or coolant can enter the transmission line and/or exit thetransmission line. In some embodiments, one or more of the towerassemblies 110 can include an intermediate cooling station (ICS).

In some embodiments, the conductor assembly 120 can include a suspendedconductor assembly (SCA), such that the conductor assembly 120 issuspended aboveground. In other words, the tower assembly 110A can bephysically coupled to the tower assembly 110B via an SCA. In someembodiments, the electrical coupling between the power transmissionsystem 100 and the external power grid or other external power sourcecan include an SCA. In some embodiments, the electrical coupling betweenthe power transmission system 100 and the one or more consumer loads canbe via an SCA. In some embodiments, the SCAs described herein caninclude superconducting OH power transmission lines.

As shown, the power transmission system 100 includes one coolant supplysystem 130. In some embodiments, the power transmission system 100 caninclude multiple coolant supply systems 130. In some embodiments, thepower transmission system 100 can include any number of coolant supplysystems 130, depending upon the application and/or the distance overwhich the power is to be transmitted. In some embodiments, the powertransmission system 100 can include at least about 1, at least about 2,at least about 3, at least about 4, at least about 5, at least about 6,at least about 7, at least about 8, at least about 9, at least about 10,at least about 20, at least about 30, at least about 40, at least about50, at least about 60, at least about 70, at least about 80, or at leastabout 90, or at least about 100 coolant supply systems 130. In someembodiments, the power transmission system 100 can include no more thanabout 100, no more than about 90, no more than about 80, no more thanabout 70, no more than about 60, no more than about 50, no more thanabout 40, no more than about 30, no more than about 20, no more thanabout 10, no more than about 9, no more than about 8, no more than about7, no more than about 6, no more than about 5, no more than about 4, nomore than about 3, or no more than about 2 coolant supply systems 130.Combinations of the above-referenced number of coolant supply systems130 are also possible (e.g., at least about 2 and no more than about 100or at least about 10 and no more than about 50), inclusive of all valuesand ranges therebetween. In some embodiments, the power transmissionsystem 100 can include about 1, about 2, about 3, about 4, about 5,about 6, about 7, about 8, about 9, about 10, about 20, about 30, about40, about 50, about 60, about 70, about 80, about 90, or about 100coolant supply systems 130. In some embodiments, a distance betweensequential coolant supply systems 130 can be about 25 kilometers (km),or about 30 km, or about 35 km, or about 40 km, or about 45 km, or about50 km, or about 55 km, or about 60 km, or about 65 km, or about 70 km,or about 75 km, or about 80 km, or about 85 km, or about 90 km, or about95 km, or about 100 km, or between about 50 km and about 100 km, orbetween about 50 km and about 150 km.

In some embodiments, one or more of the tower assemblies 110 can be influid communication with one or more of the coolant supply systems 130.In some embodiments, the coolant supply system 130 can include a coolantstorage unit. In some embodiments, the coolant supply system 130 caninclude a conditioning unit to control coolant temperature. In someembodiments, the coolant supply system 130 can be fluidically coupled tothe tower assembly 110A (or any of the tower assemblies 110) via anassociated coolant conduit. During operation of the power transmissionsystem 100, coolant fluid can flow or be pumped from the coolant system130 to the tower assemblies 110 to cool the superconducting OH powertransmission line.

FIG. 2 illustrates a power transmission system 200, according to anembodiment. The power transmission system 200 includes tower assemblies210A, 210B, 210C (collectively referred to as tower assemblies 210),conductor assemblies 220A, 220B (collectively referred to as conductorassemblies 220), and a coolant supply system 230. In some embodiments,the tower assemblies 210, the conductor assemblies 220, and the coolantsupply system 230 can be the same or substantially similar to the towerassemblies 210, the conductor assembly 120, and the coolant supplysystem 130, as described above with reference to FIG. 1. Thus certainaspects of the tower assemblies 210, the conductor assemblies 220, andthe coolant supply system 230 are not described in greater detailherein.

As shown in FIG. 2, the power transmission system 200 is an OH powertransmission system and includes an OH power transmission line. In someembodiments, the power transmission system 200 can include asuperconducting OH transmission system. In some embodiments, the OHpower transmission line refers to a series of interconnected conductorsegments (e.g., an electrical connection 221 and the conductorassemblies 220A, 220B).

The tower assemblies 210A, 210B, 210C include towers 217A, 217B, 217C(collectively referred to as towers 217) and dielectric insulators 216A,216B, 216C (collectively referred to as dielectric insulators 216). Oneor more tower assemblies 210 includes a termination 215. In someembodiments, the termination 215 acts as a connection point via whichelectrical current can enter the conductor assemblies 220 and/or exitthe conductor assemblies 220. In some embodiments, the termination 215acts as a connection point via which coolant can enter the conductorassemblies 220 and/or exit the conductor assemblies 220.

In some embodiments, the conductor assemblies 220 can include SCAs. Theconductor assemblies 220 (described in further detail below, withreference to FIG. 3) each include at least one conductive elementenclosed in a TIJ. Depending on the implementation, each of theconductor assemblies 220 may include three conductors (e.g., for threephase AC electrical power transmission), two conductors (e.g., for DCbipole power transmission), or any other number of conductors, accordingto the design of the power transmission system. In some embodiments, theconductor assemblies 220 can collectively define a power transmissionline, an OH transmission line, and/or a superconducting OH transmissionline.

As shown in FIG. 2, the coolant supply system 230 includes a coolantstorage unit 232 configured to store coolant fluid (including liquid,gas, or a combination of liquid and gas) and/or supply coolant fluid ata specified flow rate to a conditioning unit 234. The coolant fluid caninclude, for example, liquid nitrogen, liquid helium, liquid neon,liquid hydrogen, liquid natural gas, or liquid air. The conditioningunit 234 conditions the coolant fluid (e.g., by reducing the temperatureand/or increasing the pressure of the coolant fluid) prior to thecoolant fluid entering the transmission line, and, in turn, deliversconditioned coolant fluid (including liquid, gas, or a combination ofliquid and gas) to a portion of the transmission line at a specifiedtemperature (e.g., about 77 K) and pressure (e.g., between about 10 barand about 15 bar, or between about 25 bar and about 30 bar), or attemperature that is within a specified temperature range and at apressure that is within a specified pressure range. The coolant thenflows into the conductor assemblies 220 through one or more coolantconduits 236 and the termination 215. Electrical power enters the powertransmission system 200 from an external power grid (see arrow “A” inFIG. 2) though an electrical connection 221, and commences transmissionin parallel with the coolant flow, beginning at the termination 215,through the conductor assemblies 220. The termination 215 and theconductor assemblies 220 are separated from the towers 217 by thedielectric insulators 216. During operation, the coolant fluid,electrical current and power flow along and through the conductorassemblies 220.

In some embodiments of the present disclosure, the power transmissionsystem 200 includes one or more components that extract heat from the OHpower transmission line, for example by vaporizing a portion of theflowing coolant fluid and venting the vapor from the OH powertransmission line. The heat can be generated, for example, as a resultof current flow and/or heat-in-leak from the ambient environment. In theembodiment of FIG. 2, the vaporization and venting processes areachieved using one or more intermediate cooling stations 218. In someembodiments, the vaporization of liquid coolant fluid occurs inside theOH power transmission line at multiple locations along the length of theOH power transmission line. For example, venting may occur atpole-mounted equipment similar to the intermediate cooling station 218.

In some embodiments, the coolant is liquid air, and during operation ofthe power transmission system 200, venting of associated evaporatedspecies (i.e., nitrogen, argon, oxygen) to atmosphere or the ambientenvironment can be performed. In other embodiments, employing liquidhelium or liquid neon as the coolant, spent coolant may be directed fromthe power transmission system 200 into a contained space for subsequentrepurposing/re-use (e.g., after recooling to a liquid state).

In some embodiments, the coolant includes one or more (e.g., acombination of) constituents of liquid air, such as liquid nitrogenand/or liquid oxygen. For example, a composition of the coolant caninclude nitrogen and oxygen, with the oxygen constituting a percentageof between about 0.001% and about 21% (e.g., about 1%) of the overallcomposition. In other words, the composition can include a combinationof oxygen and nitrogen, with an amount of oxygen that falls somewherebetween that of liquid air (21% oxygen) and that of pure liquid nitrogen(e.g., about 0.001% oxygen).

In some embodiments, each intermediate cooling station 218 is separatedfrom its associated tower 217B by one or more dielectric insulators 216(as shown in FIG. 2). The one or more dielectric insulators may be thesame as the dielectric insulators 216 that separate the conductorassemblies 220 from the towers 217, or the one or more dielectricinsulators may be separate dielectric insulators that support theintermediate cooling station 218 alone. In the latter case, a “jumper”coolant conduit may be used to flow nitrogen from the conductor assembly(220) to the intermediate cooling station 218. In other embodiments, theintermediate cooling station 218 may be grounded (i.e., attached to thetower 217B) without an intervening dielectric insulator. In such cases,liquid coolant may flow through the center of the dielectric insulator216 that attaches the tower assembly 210B to the tower 217B. Thedielectric insulator can facilitate transporting the liquid (which maybe non-conductive) from the high voltage environment to groundpotential.

In some embodiments, evaporative cooling and venting occur “at voltage”(i.e., at the same voltage as the operating voltage of the powertransmission system 200) within one or more of the intermediate coolingstations 218. In other embodiments, evaporative cooling and ventingoccur at ground potential within one or more of the intermediate coolingstations 218. In still other embodiments, evaporative cooling occurs atvoltage within one or more of the intermediate cooling stations 218,while venting occurs at ground potential within the one or more of theintermediate cooling stations 218.

In some embodiments, the coolant storage unit 232, the coolantconduit(s) 236, the conductor assemblies 220, and optionally theconditioning unit 234 and/or the termination 215, can collectively bereferred to as a “coolant delivery and conditioning system” (e.g., aliquid nitrogen delivery and conditioning system). In some embodiments,the coolant delivery and conditioning system (e.g., as shown anddescribed with reference to FIG. 2) is a valve-free coolant delivery andconditioning system. In other words, the coolant storage unit 232, thecoolant conduit(s) 236, the conductor assemblies 220, and optionally theconditioning unit 234 and/or the termination 215 can operate without avalve for circulation of coolant. Alternatively or in addition, in someembodiments, the coolant delivery and conditioning system includes onlyone supply of coolant fluid (e.g., coolant storage unit 232 of FIG. 2),and does not include auxiliary cooling systems along the length of theOH power transmission line. Alternatively or in addition, in someembodiments, the coolant delivery and conditioning system includesmultiple supplies of coolant fluid (e.g., coolant storage unit 232 ofFIG. 2) positioned at towers (e.g., towers 217 of FIG. 2), but does notinclude auxiliary supplies of coolant fluid along the lengths of thesuspended conductor assemblies of the power transmission line. Coolantsupply systems that include multiple supplies of coolant fluidpositioned at towers can include a supply of coolant fluid at each towerwithin the OH power transmission system. Coolant supply systems thatinclude multiple supplies of coolant fluid positioned at towers can beconfigured to cool at least some of the supplies of coolant fluidexclusively, or substantially exclusively, using the evaporation ofliquid coolant (e.g., liquid nitrogen, liquid hydrogen, liquid helium,liquid neon, liquid natural gas, or liquid air) already flowing in theOH power transmission line (e.g., delivered to the OH power transmissionline via a preceding supply of coolant fluid. Alternatively or inaddition, in some embodiments, the coolant supply system does notdischarge coolant fluid to an exterior of the OH power transmission lineat all, or does not discharge coolant fluid to an exterior of the OHpower transmission line along the lengths of the suspended conductorassemblies.

FIG. 3 shows a perspective view of a section of a conductor assembly 320(e.g., for use as a conductor assembly 120 of FIG. 1) for asuperconducting OH power transmission line/system, according to anembodiment. As shown in FIG. 3, the conductor assembly 320 includes aplurality of superconductor wires or tapes 322. The wires or tapes 322can, for example, include non-spiral wound wires or tapes (i.e., wiresor tapes laid along a surface such as a surface of a former, discussedfurther below), multiple tapes interleaved with spacers, etc. When thesuperconductor wires or tapes 322 are cooled below a ‘criticaltemperature’ (e.g., at or below −100° C.), the superconductor wires ortapes 322 can carry direct, or constant, electrical currents (i.e., DCcurrent) with no resistance or with substantially no resistance, and assuch, no heat is generated in the superconductor wires or tapes 322 fromthe DC current. Alternating, or time varying, currents (i.e., ACcurrent) can generate a small (relative to non-superconductingmaterials) amount of heat in the superconductor wires or tapes 322. Forexample, a conductor assembly 320 may generate 0.5 W/m of heat whencarrying 1,000 Arms, as contrasted with a known Aluminum conductorsteel-reinforced (“ACSR”) cable, which typically generates about 68 W/mof heat during operation.

The superconductor wires or tapes 322 may be wound on a former 324, forexample in a spiral fashion (as shown in FIG. 3), in multiple layerswith multiple superconductor wires per layer. Alternatively, thesuperconducting wires/tapes may be placed in a non-spiral manner on theformer 324. Parameters such as the number of wires/tapes per layer, thewidth or diameter of the superconductor wire/tape, the angle anddirection of winding, and the number of layers can be selected oradjusted based on a desired application, for example to minimize AClosses and/or to minimize self-inductance of the conductor assembly 320.Similarly, a number of layers with desired winding angles may beselected to produce desired mechanical and/or electrical characteristicsof the conductor assembly 320. The superconductor wires or tapes 322 andthe former 324 can collectively be referred to as a conductor core.

In some embodiments, the former 324 is hollow such that it can carrygas, vapor and/or liquid coolant fluid to assist with cooling of theconductor assembly 320. Alternatively or in addition, the former 324 maybe porous to allow the ingress or egress of liquid, vapor or gascoolant.

In some embodiments, the former 324 may carry or bear some or all of thetensile force during suspension of the conductor assembly 320 (e.g., aspart of a suspended conductor assembly).

A TIJ 326 encloses the superconductor wires or tapes 322 and defines acoolant flow space 328 configured to minimize an amount of heat from thesurroundings that reaches the superconductor wires or tapes 322. Duringoperation, an inner surface of the TIJ 326 can be cooled to atemperature of the coolant, while an outer surface of the TIJ 326 can beat ambient temperature, and the inner surface of the TIJ 326 can be loadbearing (i.e., providing mechanical support). Alternatively or inaddition, a separate cable or tube positioned within the TIJ 326 can beload bearing and provide mechanical support.

The TIJ 326, itself, can include, for example, two concentric metalpipes spaced from one another, with vacuum or another material (e.g.,carbon dioxide (CO2), an inert gas, etc.) disposed between the two metalpipes. As another example, the TIJ 326 may include two concentric metalpipes, rendered flexible by corrugation or other means, spaced from oneanother, with vacuum or another material (e.g., an inert gas) disposedbetween the two flexible metal pipes. As yet another example, the TIJ326, itself, can include, for example, two concentric metal pipes spacedfrom one another, with vacuum or another material (e.g., carbon dioxide(CO2), an inert gas, etc.) disposed between the two metal pipes, andwith a spacing and/or material of the concentric metal pipes renderingthe TIJ 326 semi-rigid. The phrase “semi-rigid,” as used herein, canrefer to the property of being able to bend slightly (e.g., to a radiusof curvature of no less than 10 meters) under a mechanical load. In someembodiments, the TIJ can include another type of thermal insulation,such as expanded foam. The TIJ 326 can be manufactured in segmentshaving lengths that are appropriate for shipping, transport andinstallation.

In some embodiments, an interior surface of the TIJ 326 is configured to(or has mechanical/materials properties such that it will) thermallycontract upon being cooled to an operating temperature. This contractioncan be significant, for example if the operating temperature is below−100° C. An exterior wall of the TIJ 326 can be configured to (or havemechanical/materials properties such that it will) accommodate thereduction in length of the interior surface of the TIJ 326, along withthe other elements of the conductor assembly 320. In someimplementations, one or more elements providing the tensile strength ofthe conductor assembly 320 are selected such that they exhibit acontraction that is similar to, or that matches, the thermal contractionof the inner wall of the TIJ 326. In such implementations, the conductorassembly 320 can be installed between poles or towers supporting the OHpower transmission line at ambient temperatures with a specifiedpre-calculated tension. This tension results in an acceptable sag of theconductor assembly 320 between the poles/towers, and an acceptableclosest approach to ground level. During operation, and upon beingcooled to the operating temperature, the conductor assembly 320 (undertension) contracts, the mechanical tension of the conductor assembly 320increases, and the sag decreases. The tension at operating temperatureis thereafter maintained within acceptable limits for use in powertransmission lines.

In some embodiments, the coolant flow space 328 is filled with a flowingliquid coolant. If the superconductor wires or tapes 322 include one ormore cryogenically cooled superconductors, the liquid coolant can be aliquid cryogen (e.g., liquid nitrogen, liquid hydrogen, liquid helium,liquid neon, liquid natural gas, or liquid air). In cryogenicembodiments, the heat energy entering the conductor assembly 320 fromthe surroundings should be minimized, to minimize the coolingrequirements. This can be accomplished by, for example, using adouble-walled vacuum insulated pipeline as the TIJ 326.

In some embodiments, when used in the context of a superconducting OHpower transmission (or and/or distribution) system, the conductor core(i.e., the superconductor wires or tapes 322 and the former 324), thecoolant and the TIJ 326 are maintained at the system operating voltage.

In some embodiments, the TIJ 326 is not dielectrically insulated using asolid insulation material. Instead, air can be used as insulation,similar to the manner in which air can be used to dielectricallyinsulate known transmission conductors, if the system is designed suchthat the thermally insulating member(s) operate at the same voltage asthe conductor(s). Previous attempts to develop superconducting cableswith a “warm dielectric,” in which the thermal insulating members areoperated at line voltage, pertained to underground applications andrequired external solid insulation. Such solid insulators are notincluded in embodiments of the present disclosure.

As discussed above, in some embodiments, suspended conductor assembliesare attached to the towers using one or more dielectric insulators. Insome such embodiments, the dielectric insulators are configured totransport liquid nitrogen and/or vapor nitrogen from one or more highvoltage regions of the superconducting OH power transmission system toground potential. Heat that enters the TIJ 326 or that is generated byelectrical energy losses and/or magnetic energy losses inside the TIJ326 should be removed from the superconducting OH power transmissionsystem to ensure that an appropriate operating temperature ismaintained. Intermediate cooling stations disposed on one or more towersof the superconducting OH power transmission system can be used toaccomplish this. If the intermediate cooling station(s) produce excessvapor by utilizing boiling coolant, this excess can be vented toatmosphere.

In some embodiments, multiple conductor assemblies as shown in FIG. 3are supported by poles or towers to maintain an adequate clearancebetween the conductor assemblies and the ground. The spacing between thepoles or towers and the tensile strength of the conductor assemblies canbe selected such that a desired suspension can be maintained throughoutoperation. Tensile forces on the conductor assemblies can becarried/borne by one or more components of the superconducting OH powertransmission system, such as the former 324, the inner wall of the TIJ326, and/or an additional force carrying member (such as steel rope orwire), that are disposed within a cooled region of the superconductingOH power transmission system.

Each conductor assembly 320 can be installed in an un-cooled (i.e.,ambient temperature) state between a pair of poles, and will exhibit afirst curvature (e.g., a catenary) when suspended. The first curvaturecan be described as a first sag, which depends on the tension forcesexerted at the poles. When coolant begins to flow within the conductorassemblies 320, the internal temperature of the conductor assemblies 320decreases and, due to thermal contraction, the element(s) of theconductor assemblies 320 that bear the tensile forces contract or becomeshorter. This contraction causes a reduction in the sag, resulting in asecond curvature different from (and shallower than) the firstcurvature, and the tension forces increase. The decrease in length ofthe element(s) can be, for example, about 0.5%, for example forconductor assemblies that are cooled using liquid nitrogen. As discussedabove, in some embodiments, all components disposed within the cooledregion of the superconducting OH power transmission system areconfigured to (or have mechanical or material properties such that they)contract in length similarly. In other words, the difference in thermalcontraction between installation ambient temperature and operatingtemperature is less than that which would result in a permanentdeformation of one or more of the components. For example, if one of thecomponents is placed under tensile stress by a differential contraction,the stress may be less than a quarter of the yield stress (assuming anengineering safety factor of 4 is appropriate for the application). Indirect contrast with known systems, superconducting OH powertransmission lines of the present disclosure exhibit the same sag (orsubstantially the same lag), and hence the same clearance to ground (orsubstantially the same clearance to ground), under all electrical loadsand environmental temperatures.

In some embodiments, all components disposed within the cooled region ofthe superconducting OH power transmission system are fabricated from thesame type of material.

The capacitance of a power transmission line is one of the parametersthat determines the operating characteristics of the power transmissionline in an AC grid, and that influences the surge impedance loading(i.e., the ratio of the amplitudes of voltage and current of a singlewave propagating along the power transmission line). The capacitance ofa power transmission line can be determined by integrating the electricfield from the outer envelope of the power transmission line to an upperlimit distance determined by the placement of other phases of thecircuit and/or the ground. The electric field near a conductor varies asl/r (r being the distance from the center of a conductor), andconsequently, the radius of the ‘at voltage’ envelope significantlydetermines the capacitance. The assembly of FIG. 3, with the outer wallof the TIJ 326 maintained at the system operating voltage, has acapacitance that is lower than that of known power transmission lines,which offers operational advantages.

FIG. 4 shows a perspective view of a section of a conductor assembly 420for a superconducting OH power transmission line/system, includingelectrical insulation 427 (e.g., cross-linked polyethylene (“XLPE”) orpolypropylene laminated paper (“PPLP”) adjacent to one or moresuperconductors (superconductor wires or tapes 422) and disposed withina TIJ 426, according to an embodiment. The TIJ 426 defines a coolantflow space 428 configured to minimize an amount of heat from thesurroundings that reaches the superconductor wires or tapes 422. Asshown in FIG. 4, the electrical insulation 427 is disposed fully withinthe TIJ 426 such that the electrical insulation 427 is cooled to thesuperconductor operating temperature during operation of thesuperconducting OH power transmission line/system. The embodiment ofFIG. 4 can be referred to as a “cold dielectric design.” The thicknessof the electrical insulation 427 can be selected to ensure that allother components within the TIJ 426 are maintained at ground potentialwithout the risk of short-circuiting. In the embodiment of FIG. 4, thereis no electric field away from the conductor (i.e., the magnitude of theelectric field vector, irrespective of the direction of the fieldvector, is zero). Superconducting OH power transmission lines using oneor more conductor assemblies of FIG. 4 can be referred to as “minimalfire hazard” power lines, in that any objects coming into contact withthe power line (e.g., tree branches, vegetation) will not form a shortcircuit to ground, and will not ignite fuel. In other embodiments, thethickness of the electrical insulation 427 may be selected at a levelthat achieves less than full electrical insulation (i.e., partialelectrical insulation), in which case the electrical insulation 427presents a high resistivity barrier to an electrical short circuitreducing the fault current flowing. Superconducting OH powertransmission lines using one or more such conductor assemblies can bereferred to as “reduced fire hazard” power lines.

FIG. 5 shows a perspective view of a section of a conductor assembly 520for a superconducting OH power transmission line/system, includingelectrical insulation 527 disposed exterior to a TIJ 526, according toan embodiment. The TIJ 526 defines a coolant flow space 528 configuredto minimize an amount of heat from the surroundings that reaches thesuperconductor wires or tapes 522. Because the electrical insulation 527is outside the TIJ 526, the electrical insulation 527 is not cooled tothe superconductor operating temperature during operation of thesuperconducting OH power transmission line/system. As such, theembodiment of FIG. 5 can be referred to as a “warm dielectric” design.The thickness of the electrical insulation 527 can be selected such thatthe conductor assembly 520 can come into contact with a ground potentialwithout risk of a short circuit. Similar to conductor assembly 420 ofFIG. 4, there is no electric field away from the conductor assembly 520of FIG. 5. Superconducting OH power transmission lines using one or moreconductor assemblies of FIG. 5 can be referred to as “minimal firehazard” power lines, in that any objects coming into contact with thepower line (e.g., tree branches, vegetation) will not form a shortcircuit to ground, and will not ignite fuel.

In some embodiments, an electrically conducting layer (not shown) isapplied to at least a portion of (e.g., an entire exterior surface of)the electrical insulation 527 in the embodiment of FIG. 5. Theelectrically conducting layer can include, for example, asuperconducting winding or a non-superconducting winding. Theelectrically conducting layer can be electrically grounded, or can beelectrically connected to a nonzero potential such that the conductinglayer carries a current that is equal to (or substantially equal to),but of opposite polarity (e.g., instantaneous AC or AC) as comparedwith, the current in the conductor core (which includes thesuperconductor wires or tapes 522 and the former 524). When theelectrically conducting layer is electrically grounded or connected to anonzero potential as discussed above, the operation of the conductorassembly 520 does not result in any electric field or magnetic fieldoutside the TIJ 526. Superconducting OH power transmission lines usingone or more such conductor assemblies of FIG. 5 can be referred to as“zero external electromagnetic field (“EMF”)” power lines.

In some embodiments, an outer electrically conducting layer (referred toherein as a “shield layer”) is applied to at least a portion of (e.g.,an entire exterior surface of) the electrical insulation 527 in theembodiment of FIG. 5. The outer electrically conducting layer caninclude, for example, a superconducting winding or a non-superconductingwinding. During operation of a power line including the conductorassembly 520, the current flowing in the shield layer can be controlled,to control the self-inductance of the AC power line. For example, if theshield layer carries a current that is equal in magnitude and oppositein polarity to the current of the conductor core, there is no magneticfield outside the power line and the self-inductance of the power lineis minimized. Conversely, reducing the shield current using an externalmeans can cause the self-inductance of the power line to increase. Assuch, the power flow in the grid and/or power line can advantageously becontrolled. The shield layer may be placed along the entire length of,or a portion of the length of, the power line.

In some embodiments, an outer conducting layer (referred to herein as a“shield layer”) is applied to at least a portion of (e.g., an entireexterior surface of) the electrical insulation 527 in the embodiment ofFIG. 5. The outer conducting layer can include, for example, asuperconducting winding or a non-superconducting winding. In addition, amaterial having a magnetic permeability greater than unity is placedoutside the shield layer. During operation of a power line including theconductor assembly 520, if the shield layer carries a current that isequal in magnitude and opposite in polarity to the current of theconductor core, no magnetic field will impinge on the magnetic layer,and the self-inductance of the power line is minimized. Conversely,reducing the shield current using an external means allows the magneticfield to interact with the magnetic material, thereby significantlyincreasing the self-inductance of the power line. As such, the powerflow in the grid and/or power line can advantageously be controlled. Theshield layer and/or the magnetic material may be placed along the entirelength of, or a portion of the length of, the power line.

Although shown and described in FIG. 5 as including a single conductorcore within the TIJ 526, the conductor assembly 520 can alternativelyinclude multiple (e.g., two, three, four, five, or between five and ten)conductor cores within the same TIJ 526. For example, two conductorcores may be included within a TIJ 526 of the conductor assembly 520,for example as the two poles of a DC bipole system. As another example,three conductor cores may be included within a TIJ 526 of the conductorassembly 520, for example as the three phases of a 3-phase AC powertransmission system.

FIG. 6 shows a perspective view of a short section of a conductorassembly 620 for use in a superconducting OH power transmissionline/system (e.g., similar to the superconducting OH power transmissionsystem of FIG. 1) using a “distributed cooling” approach. The conductorassembly includes a coolant tube 629 for carrying liquid coolant (e.g.,liquid nitrogen, liquid helium, liquid neon, liquid hydrogen, liquidnatural gas, or liquid air) at a pressure greater than a pressure of thecoolant flow space 628 defined by the TIJ 626. Coolant tube 629 can bemanufactured to include a plurality of pores or orifices, for exampleoccurring at specified intervals along the length of the coolant tube629. During operation of the conductor assembly 620, liquid coolant canexit the coolant tube 629 through the pores or orifice, and enter intothe coolant flow space 628, such that the coolant flow space 628contains coolant vapor and liquid—a two-phase (biphasic) fluid. Heatleaking into the coolant flow space 628 or generated within the TIJ 326will cause the temperature of the two-phase fluid to increase until itreaches the boiling point of the liquid coolant at the local pressure inthe coolant flow space 628. Consequently, the coolant liquid in thecoolant flow space 628 will boil and maintain the cooled region at thelocal pressure-dependent boiling temperature (or “saturationtemperature”) of the coolant if enough coolant is present. As anexample, when the coolant is liquid nitrogen and the coolant flow space628 is at atmospheric pressure, the saturation temperature isapproximately −196° C. (77K).

In an alternative implementation of the conductor assembly 620 of FIG.6, liquid coolant may flow in the coolant flow space 628 and enter thecoolant tube 629 via the plurality of pores or orifices (e.g., at thespecified intervals). During operation of the conductor assembly 620,heat is transferred to the coolant tube 629 from the liquid coolant inthe coolant flow space 628, via conduction and/or convection, therebycausing the liquid coolant in the coolant tube 629 to boil, in whichcase the coolant tube 629 will carry coolant vapor at the saturationtemperature.

Although shown and described with reference to FIG. 6 as being disposedwithin the coolant flow space 628, in other embodiments, the coolanttube 629 may be disposed within the former 624 of the conductor core. Instill other embodiments, the coolant tube 629 may be omitted, and theformer 624 may serve as a coolant tube. The coolant tube 629 may beconfigured to support, or bear, all or a portion of the tensile forcesof suspension of the conductor.

In some embodiments, during operation of a conductor assembly includinga coolant tube (such as the coolant tube 629 of FIG. 6), vapor isgenerated along the entire length of the conductor assembly. In suchembodiments, separate tower-mounted intermediate cooling stations maynot be used within the associated power transmission system. In suchembodiments, tower-mounted equipment may still be positioned atlocations along the power transmission line, but the role of suchtower-mounted equipment may be primarily to remove vapor from theconductor assembly and prepare it for venting, and not to generatevapor.

In some embodiments, a power transmission line includes a distributedcooling system that does not incorporate a coolant supply at eitherterminal end of the power transmission line. Rather, all coolant fluid(e.g., liquid nitrogen, liquid helium, liquid neon, liquid hydrogen,liquid natural gas, or liquid air) is introduced to, and consumed by(e.g., via evaporation and/or venting), the power transmission linealong its multiple constituent suspended conductor assemblies (all LN2is utilized/evaporated along the line length for cooling) via one ormore coolant supplies (e.g., intermediate cooling stations). Optionally,one or more of the intermediate cooling stations is configured tofacilitate the flow of coolant in both directions within the powertransmission line. For example, if an individual coolant supply isconfigured to supply coolant over a distance of 25 km, a first instanceof that individual coolant supply may be positioned at a location alongthe power transmission line that is 25 km from a first terminal end ofthe power transmission line, such that it supplies coolant over adistance of 25 km back toward the first terminal end of the powertransmission line (i.e., in a first direction) and forward over adistance of 25 km along the power transmission line (i.e., in a seconddirection opposite the first direction). If the power transmission lineis sufficiently long, a second instance of the individual coolant supplymay be positioned at a location along the power transmission line thatis 75 km from the first terminal end of the power transmission line.(thereby supplying coolant for the section of the power transmissionline between 50 km and 100 km from the first terminal end of the powertransmission line).

In some embodiments, a power transmission line includes a distributedcooling system that incorporates a coolant supply at one terminal end ofthe power transmission line, but not at the other terminal end of thepower transmission line, to introduce coolant fluid to the powertransmission line. In addition, coolant fluid (e.g., liquid nitrogen,liquid helium, liquid neon, liquid hydrogen, liquid natural gas, orliquid air) is introduced to, and consumed by (e.g., via evaporationand/or venting), the power transmission line along its multipleconstituent suspended conductor assemblies (all LN2 isutilized/evaporated along the line length for cooling).

In some embodiments, a distributed cooling system (e.g., including theconductor assembly 620 of FIG. 6, having a coolant tube and generatingvapor inside the conductor assembly) is controlled such that there is noremaining nitrogen flow at the end of each section, and thus no coolantaccumulates at the end of the power transmission line.

In some embodiments, a periodic cooling system (i.e., a cooling systemthat generates vapor at heat exchangers located inside the towerassemblies) has a non-zero coolant flow at the ends of the coolingstations. To manage such coolant flow, the coolant may be transported inonly one direction from a first coolant supply location, and the end ofone section of the power transmission line may be located at a secondcoolant supply location for a next section of the power transmissionline. In such a configuration, excess coolant from the first section ofthe power transmission line flows into one or multiple coolant storagetanks at the second coolant supply location and can eventually bereconditioned and used for cooling the next section of the powertransmission line. Excess liquid nitrogen at the remote terminal end ofthe power transmission line may be repurposed, stored, transported awayfrom the terminal end of the power transmission line (e.g., by truck toone of the coolant supply locations), and/or evaporated to the air atthat location.

In other embodiments, a periodic cooling system is configured tofacilitate coolant flow, from each coolant supply location, in bothdirections along the power transmission line, in one pole (for DCapplications) or 2 phases (in AC applications), and the subsequentreturn of the coolant back to the coolant supply location in the otherpole (DC) or the third phase (AC), thereby eliminating the need tocapture and manage excess coolant flows at the end(s) of the powertransmission line.

In some embodiments, a power transmission system includes one or morethermal insulation jackets, to maintain the superconductor at a lowtemperature, and one or more dielectric insulators. In otherembodiments, a power transmission system includes one or more thermalinsulation jackets, to maintain the superconductor at a low temperature,but does not include dielectric insulators. In such embodiments, air mayprovide dielectric insulation.

In some embodiments, a power transmission system includes multiplesupport towers, each extending from a surface of the earth along adirection normal to the surface of the earth, and multiple conductorassemblies. Each conductor assembly is disposed between and mechanicallysupported, in a suspended configuration, by a pair of the supporttowers, and each conductor assembly includes an electrical conductorincluding a superconductor material. Each conductor assembly isconfigured to receive a coolant flow to maintain the superconductormaterial within a temperature range below an ambient temperature. Eachconductor assembly can include a thermal insulation jacket configured tocontain the coolant flow, the thermal insulation jacket not beingelectrically isolated from an operating voltage of the powertransmission system.

In some embodiments, each conductor assembly further includes a thermalinsulation jacket having an inner/interior surface that is maintained ata temperature similar to a temperature of the electrical conductor(while an outer/exterior surface of the thermal insulation jacket ismaintained at ambient temperature), the thermal insulation jacket beingconfigured to mechanically support the associated conductor assembly. Inaddition, the thermal insulation jacket may be maintained at a voltagethat is equal to a voltage of the electrical conductor. The thermalinsulation jacket can include one or more of vacuum, an inert gas, or aninsulating foam.

In some embodiments, the power transmission system also includes aplurality of mechanical supports, each mechanical support from theplurality of mechanical supports configured to mechanically support aconductor assembly from the plurality of conductor assemblies.

In some embodiments, each conductor assembly from the plurality ofconductor assemblies further includes a thermal insulation jacket and adielectric insulator disposed between the electrical conductor and thethermal insulation jacket, the dielectric insulator including a soliddielectric material (e.g., XLPE or PPLP).

In some embodiments, each conductor assembly from the plurality ofconductor assemblies further includes a thermal insulation jacket havinga dielectric insulator disposed between two concentric walls, thedielectric insulator including a solid dielectric material (e.g., XLPEor PPLP).

In some embodiments, each conductor assembly from the plurality ofconductor assemblies further includes a thermal insulation jacket and adielectric insulator, the dielectric insulator disposed between an outersurface of the thermal insulation jacket and an outer surface of theconductor assembly. In other embodiments, each conductor assembly fromthe plurality of conductor assemblies further includes a thermalinsulation jacket and a dielectric insulator, the dielectric insulatorbeing an outermost component of the conductor assembly such that anouter surface of the dielectric insulator is the outer surface of theconductor assembly.

In some embodiments, a power transmission system includes multiplesupport tower assemblies, multiple conductor assemblies suspended abovea surface of earth, and a cryogenic supply system (e.g., a liquidnitrogen supply system). Each of the support tower assemblies includes asupport tower and a termination. Each of the conductor assemblies isdisposed between and mechanically supported by a pair of the supporttowers. The cryogenic supply system is configured to deliver a cryogen(e.g., including at least one of liquid nitrogen, liquid hydrogen,liquid helium, liquid neon, liquid natural gas, or liquid air), duringoperation of the power transmission system, to at least one of theterminations for cooling of the conductor assemblies. Each of theconductor assemblies includes a superconducting current carrying element(e.g., superconductor-containing wires or superconductor-containingtapes) and a thermal insulation jacket configured to receive a flowingcoolant that maintains a temperature of the superconductor materialwithin a temperature range that is below an ambient temperature. Thethermal insulation jacket can be configured to contain the coolantwithin the conductor assembly, and direct or manage the flow of thecoolant. The thermal insulation jacket can also reduce or limit theamount of ambient heat that reaches the coolant. The coolant can includeone or more cryogens. The coolant can protect the superconductingcurrent carrying elements from heat during operation of the powertransmission system, for example by absorbing heat entering the powertransmission system from the environment and/or by absorbing heatgenerated within the conductor assemblies. Heat generated within theconductor assemblies can be due, for example, to power flow, coolantflow, energy losses within insulating materials (e.g., dielectriclosses) due to varying voltages, energy losses in conductive materialsdue to varying magnetic fields (e.g., eddy current losses), and/orenergy losses in magnetic materials due to varying magnetic fields(e.g., magnetic hysteresis losses).

In some embodiments, at least one of the thermal insulation jackets isnot electrically isolated from an operating voltage of the powertransmission system. In other embodiments, at least one of the thermalinsulation jackets is electrically grounded and a dielectric insulatoris disposed between the electrical conductor and the thermal insulationjacket.

In some embodiments, at least one of the support tower assembliesincludes an intermediate cooling station configured to vent vaporproduced by the cryogen during operation of the power transmissionsystem.

In some embodiments, the cryogenic supply system includes a conditioningunit to supply the cryogen to the terminations, and to measure or adjusta temperature of the cryogen as it flows therethrough.

In some embodiments, at least one of the thermal insulation jacketsincludes a tensile support element configured to mechanically supportthe associated suspended conductor assembly.

In some embodiments, each of the conductor assemblies is connected to anassociated support tower assembly from the plurality of support towerassemblies via an insulator, the insulator providing electricalisolation of the conductor assembly from the associated support towerassembly.

In some embodiments, the conductor assemblies form a transmission line,and the cryogen flows along a direction parallel to the transmissionline during operation of the power transmission system.

In some embodiments, a power transmission system includes multiplesupport tower assemblies, multiple conductor assemblies suspended abovea surface of earth, and a coolant supply system. Each of the supporttower assemblies includes a support tower and a termination. Each of theconductor assemblies is disposed between and mechanically supported by apair of the support towers. The coolant supply system is configured todeliver coolant (e.g., liquid nitrogen, liquid hydrogen, liquid helium,liquid neon, liquid natural gas, or liquid air), during operation of thepower transmission system, to at least one of the terminations forcooling of the conductor assemblies. Each of the conductor assembliesincludes a superconducting current carrying element (e.g.,superconductor-containing wires or superconductor-containing tapes) anda thermal insulation jacket to contain the coolant during operation ofthe power transmission system. The coolant maintains the superconductingcurrent carrying elements within a temperature range below an ambienttemperature.

Depending on the embodiment, terminations of the present disclosure canbe of one of three different types: a terminal end termination (i.e.,disposed at a terminal end of a power transmission line), a re-coolingtermination, or a “pass-through” termination (i.e., permitting power andcoolant to flow therethrough, but not supplying coolant and notterminating the power transmission line).

In some embodiments, the power transmission system also includes one ormore re-cooling stations configured to modify a temperature (and,optionally, a pressure) of the coolant. Each such re-cooling station canbe maintained at an operating voltage of the power transmission systemand isolated from a ground potential. Alternatively, each suchre-cooling station can be maintained at a ground potential.

In some embodiments, at least one of the support tower assembliesincludes an intermediate cooling station to vent vapor produced by aliquid cryogen (e.g., at least one of liquid nitrogen, liquid hydrogen,liquid helium, liquid neon, liquid natural gas, or liquid air) duringoperation of the power transmission system.

In some embodiments, each thermal insulation jacket includes a thermalinsulator disposed between two concentric walls, the thermal insulatorincluding at least one of vacuum, an inert gas, or an insulating foam.

All combinations of the foregoing concepts and additional conceptsdiscussed herewithin (provided such concepts are not mutuallyinconsistent) are contemplated as being part of the subject matterdisclosed herein. The terminology explicitly employed herein that alsomay appear in any disclosure incorporated by reference should beaccorded a meaning most consistent with the particular conceptsdisclosed herein.

The drawings are primarily for illustrative purposes, and are notintended to limit the scope of the subject matter described herein. Thedrawings are not necessarily to scale; in some instances, variousaspects of the subject matter disclosed herein may be shown exaggeratedor enlarged in the drawings to facilitate an understanding of differentfeatures. In the drawings, like reference characters generally refer tolike features (e.g., functionally similar and/or structurally similarelements).

The entirety of this application (including the Cover Page, Title,Headings, Background, Summary, Brief Description of the Drawings,Detailed Description, Embodiments, Abstract, Figures, Appendices, andotherwise) shows, by way of illustration, various embodiments in whichthe embodiments may be practiced. The advantages and features of theapplication are of a representative sample of embodiments only, and arenot exhaustive and/or exclusive. Rather, they are presented to assist inunderstanding and teach the embodiments, and are not representative ofall embodiments. As such, certain aspects of the disclosure have notbeen discussed herein. That alternate embodiments may not have beenpresented for a specific portion of the innovations or that furtherundescribed alternate embodiments may be available for a portion is notto be considered to exclude such alternate embodiments from the scope ofthe disclosure. It will be appreciated that many of those undescribedembodiments incorporate the same principles of the innovations andothers are equivalent. Thus, it is to be understood that otherembodiments may be utilized and functional, logical, operational,organizational, structural and/or topological modifications may be madewithout departing from the scope and/or spirit of the disclosure. Assuch, all examples and/or embodiments are deemed to be non-limitingthroughout this disclosure.

Also, no inference should be drawn regarding those embodiments discussedherein relative to those not discussed herein other than it is as suchfor purposes of reducing space and repetition. For instance, it is to beunderstood that the logical and/or topological structure of anycombination of any program components (a component collection), othercomponents and/or any present feature sets as described in the figuresand/or throughout are not limited to a fixed operating order and/orarrangement, but rather, any disclosed order is exemplary and allequivalents, regardless of order, are contemplated by the disclosure.

The term “determining” encompasses a wide variety of actions and,therefore, “determining” can include calculating, computing, processing,deriving, investigating, looking up (e.g., looking up in a table, adatabase or another data structure), ascertaining and the like. Also,“determining” can include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” can include resolving, selecting, choosing, establishingand the like.

The phrase “based on” does not mean “based only on,” unless expresslyspecified otherwise. In other words, the phrase “based on” describesboth “based only on” and “based at least on.”

Various concepts may be embodied as one or more methods, of which atleast one example has been provided. The acts performed as part of themethod may be ordered in any suitable way. Accordingly, embodiments maybe constructed in which acts are performed in an order different thanillustrated, which may include performing some acts simultaneously, eventhough shown as sequential acts in illustrative embodiments. As such,some of these features may be mutually contradictory, in that theycannot be simultaneously present in a single embodiment. Similarly, somefeatures are applicable to one aspect of the innovations, andinapplicable to others.

In addition, the disclosure may include other innovations not presentlydescribed. Applicant reserves all rights in such innovations, includingthe right to embodiment such innovations, file additional applications,continuations, continuations-in-part, divisional s, and/or the likethereof. As such, it should be understood that advantages, embodiments,examples, functional, features, logical, operational, organizational,structural, topological, and/or other aspects of the disclosure are notto be considered limitations on the disclosure as defined by theembodiments or limitations on equivalents to the embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

As used herein, in particular embodiments, the terms “about” or“approximately” when preceding a numerical value indicates the valueplus or minus a range of 10%. Where a range of values is provided, it isunderstood that each intervening value, to the tenth of the unit of thelower limit unless the context clearly dictates otherwise, between theupper and lower limit of that range and any other stated or interveningvalue in that stated range is encompassed within the disclosure. Thatthe upper and lower limits of these smaller ranges can independently beincluded in the smaller ranges is also encompassed within thedisclosure, subject to any specifically excluded limit in the statedrange. Where the stated range includes one or both of the limits, rangesexcluding either or both of those included limits are also included inthe disclosure.

The indefinite articles “a” and “an,” as used herein in thespecification and in the embodiments, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theembodiments, should be understood to mean “either or both” of theelements so conjoined, i.e., elements that are conjunctively present insome cases and disjunctively present in other cases. Multiple elementslisted with “and/or” should be construed in the same fashion, i.e., “oneor more” of the elements so conjoined. Other elements may optionally bepresent other than the elements specifically identified by the “and/or”clause, whether related or unrelated to those elements specificallyidentified. Thus, as a non-limiting example, a reference to “A and/orB”, when used in conjunction with open-ended language such as“comprising” can refer, in one embodiment, to A only (optionallyincluding elements other than B); in another embodiment, to B only(optionally including elements other than A); in yet another embodiment,to both A and B (optionally including other elements); etc.

As used herein in the specification and in the embodiments, “or” shouldbe understood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the embodiments, “consisting of,” will refer to the inclusion ofexactly one element of a number or list of elements. In general, theterm “or” as used herein shall only be interpreted as indicatingexclusive alternatives (i.e. “one or the other but not both”) whenpreceded by terms of exclusivity, such as “either,” “one of,” “only oneof” or “exactly one of.” “Consisting essentially of,” when used in theembodiments, shall have its ordinary meaning as used in the field ofpatent law.

As used herein in the specification and in the embodiments, the phrase“at least one,” in reference to a list of one or more elements, shouldbe understood to mean at least one element selected from any one or moreof the elements in the list of elements, but not necessarily includingat least one of each and every element specifically listed within thelist of elements and not excluding any combinations of elements in thelist of elements. This definition also allows that elements mayoptionally be present other than the elements specifically identifiedwithin the list of elements to which the phrase “at least one” refers,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, “at least one of A and B” (or,equivalently, “at least one of A or B,” or, equivalently “at least oneof A and/or B”) can refer, in one embodiment, to at least one,optionally including more than one, A, with no B present (and optionallyincluding elements other than B); in another embodiment, to at leastone, optionally including more than one, B, with no A present (andoptionally including elements other than A); in yet another embodiment,to at least one, optionally including more than one, A, and at leastone, optionally including more than one, B (and optionally includingother elements); etc.

In the embodiments, as well as in the specification above, alltransitional phrases such as “comprising,” “including,” “carrying,”“having,” “containing,” “involving,” “holding,” “composed of,” and thelike are to be understood to be open-ended, i.e., to mean including butnot limited to. Only the transitional phrases “consisting of” and“consisting essentially of” shall be closed or semi-closed transitionalphrases, respectively, as set forth in the United States Patent OfficeManual of Patent Examining Procedures, Section 2111.03.

1. A power transmission system, comprising: a plurality of supporttowers; and a plurality of conductor assemblies suspended above asurface of earth, each conductor assembly from the plurality ofconductor assemblies disposed between and mechanically supported by apair of support towers from the plurality of support towers, eachconductor assembly including an electrical conductor including asuperconductor material and configured to receive a coolant flow tomaintain the superconductor material within a temperature range below anambient temperature.
 2. The power transmission system of claim 1,wherein each conductor assembly further includes a thermal insulationjacket configured to contain the coolant flow, the thermal insulationjacket not being electrically isolated from an operating voltage of thepower transmission system.
 3. The power transmission system of claim 1,wherein each conductor assembly further includes a thermal insulationjacket having an inner surface that is maintained at a temperaturesimilar to a temperature of the electrical conductor, the thermalinsulation jacket being configured to mechanically support theassociated conductor assembly.
 4. The power transmission system of claim1, further comprising a plurality of mechanical supports, eachmechanical support from the plurality of mechanical supports configuredto mechanically support a conductor assembly from the plurality ofconductor assemblies.
 5. The power transmission system of claim 1,wherein each conductor assembly from the plurality of conductorassemblies further includes a thermal insulation jacket and a dielectricinsulator disposed between the electrical conductor and the thermalinsulation jacket, the dielectric insulator including one of across-linked polyethylene (XLPE) or a polypropylene laminated paper(PPLP).
 6. The power transmission system of claim 1, wherein eachconductor assembly from the plurality of conductor assemblies furtherincludes a thermal insulation jacket having a dielectric insulatordisposed between two concentric walls, the dielectric insulatorincluding at least one of XLPE or PPLP.
 7. The power transmission systemof claim 1, wherein each conductor assembly from the plurality ofconductor assemblies further includes a thermal insulation jacket and adielectric insulator, the dielectric insulator disposed between an outersurface of the thermal insulation jacket and an outer surface of theconductor assembly.
 8. The power transmission system of claim 1, whereineach conductor assembly further includes a thermal insulation jacketthat is electrically grounded and a dielectric insulator disposedbetween the electrical conductor and the thermal insulation jacket. 9.The power transmission system of claim 1, wherein at least one supporttower from the plurality of support towers includes an intermediatecooling station configured to vent vapor produced by a liquid cryogenduring operation of the power transmission system.
 10. A powertransmission system, comprising: a plurality of support towerassemblies, each support tower assembly from the plurality of supporttower assemblies including a support tower and a termination from aplurality of terminations; a plurality of conductor assemblies suspendedabove a surface of earth, each conductor assembly from the plurality ofconductor assemblies disposed between and mechanically supported by apair of support towers from the plurality of support towers; and acryogenic supply system configured to deliver a cryogen during operationof the power transmission system, to at least one termination from theplurality of terminations for cooling of the conductor assemblies, eachconductor assembly from the plurality of conductor assemblies includinga superconducting current carrying element and a thermal insulationjacket through which the cryogen flows to maintain a temperature of thesuperconducting current carrying element within a temperature range thatis below an ambient temperature.
 11. The power transmission system ofclaim 10, wherein the cryogen includes at least one of liquid nitrogen,liquid hydrogen, liquid helium, liquid neon, liquid natural gas, orliquid air.
 12. The power transmission system of claim 10, wherein atleast one of the thermal insulation jackets is not electrically isolatedfrom an operating voltage of the power transmission system.
 13. Thepower transmission system of claim 10, wherein at least one of thethermal insulation jackets is electrically grounded.
 14. The powertransmission system of claim 10, wherein the superconducting currentcarrying element includes one of a plurality ofsuperconductor-containing wires or a plurality ofsuperconductor-containing tapes.
 15. The power transmission system ofclaim 10, wherein at least one support tower assembly from the pluralityof support tower assemblies includes an intermediate cooling stationconfigured to vent vapor produced by the cryogen during operation of thepower transmission system.
 16. The power transmission system of claim10, wherein the cryogenic supply system comprises a conditioning unitconfigured to supply the cryogen to the at least one termination fromthe plurality of terminations at a selected temperature and pressure.17. The power transmission system of claim 10, wherein at least one ofthe thermal insulation jackets mechanically supports the associatedsuspended conductor assembly.
 18. The power transmission system of claim10, wherein at least one of the thermal insulation jackets includes atensile support element disposed therewithin and configured tomechanically support the associated suspended conductor assembly. 19.The power transmission system of claim 10, wherein each conductorassembly from the plurality of conductor assemblies is connected to anassociated support tower assembly from the plurality of support towerassemblies via an insulator, the insulator providing electricalisolation of the conductor assembly from the associated support towerassembly.
 20. The power transmission system of claim 10, wherein theplurality of conductor assemblies form a transmission line, and thecryogen flows along a direction parallel to the transmission line duringoperation of the power transmission system.
 21. A power transmissionsystem, comprising: a plurality of support tower assemblies, eachsupport tower assembly from the plurality of support tower assembliesincluding a support tower and a termination from a plurality ofterminations; a plurality of conductor assemblies suspended above asurface of earth, each conductor assembly from the plurality ofconductor assemblies disposed between and mechanically supported by apair of support towers from the plurality of support towers; and acoolant supply system configured to deliver a coolant fluid, duringoperation of the power transmission system, to at least one terminationfrom the plurality of terminations for cooling of the conductorassemblies, each conductor assembly from the plurality of conductorassemblies including a superconducting current carrying element and athermal insulation jacket configured to protect the superconductingcurrent carrying element from heat during operation of the powertransmission system.
 22. The power transmission system of claim 21,further comprising a plurality of re-cooling stations configured tomodify one of a temperature or a pressure of the coolant fluid, eachre-cooling station from the plurality of re-cooling stations beingmaintained at an operating voltage of the power transmission system andisolated from a ground potential.
 23. The power transmission system ofclaim 21, further comprising a plurality of re-cooling stationsconfigured to modify one of a temperature or a pressure of the coolantfluid, each re-cooling station from the plurality of re-cooling stationsbeing maintained at a ground potential.
 24. The power transmissionsystem of claim 21, wherein at least one support tower assembly from theplurality of support tower assemblies includes an intermediate coolingstation configured to vent vapor produced by the coolant fluid duringoperation of the power transmission system.
 25. The power transmissionsystem of claim 21, wherein the coolant fluid includes one of: liquidnitrogen, liquid hydrogen, liquid helium, liquid neon, liquid naturalgas, or liquid air.
 26. The power transmission system of claim 21,wherein each thermal insulation jacket includes a dielectric insulatordisposed between two concentric walls, the dielectric insulatorincluding one of a cross-linked polyethylene (XLPE) or a polypropylenelaminated paper (PPLP).